DSSR-PyMOL cartoon-block schematics: PDB entry 7jhy

PDB-id

7jhy; DSSR-derived features in text and JSON formats

Class

immune system-RNA

Method

cryo-EM (3.9 Å)

Summary

Type iv-b crispr complex

Reference

Zhou Y, Bravo JPK, Taylor HN, Steens JA, Jackson RN, Staals RHJ, Taylor DW (2021): "Structure of a type IV CRISPR-Cas ribonucleoprotein complex." Iscience, 24, 102201. doi: 10.1016/j.isci.2021.102201.

Abstract

We reveal the cryo-electron microscopy structure of a type IV-B CRISPR ribonucleoprotein (RNP) complex (Csf) at 3.9-Å resolution. The complex best resembles the type III-A CRISPR Csm effector complex, consisting of a Cas7-like (Csf2) filament intertwined with a small subunit (Cas11) filament, but the complex lacks subunits for RNA processing and target DNA cleavage. Surprisingly, instead of assembling around a CRISPR-derived RNA (crRNA), the complex assembles upon heterogeneous RNA of a regular length arranged in a pseudo-A-form configuration. These findings provide a high-resolution glimpse into the assembly and function of enigmatic type IV CRISPR systems, expanding our understanding of class I CRISPR-Cas system architecture, and suggesting a function for type IV-B RNPs that may be distinct from other class 1 CRISPR-associated systems.